1. Field of the Invention
This invention relates to vision display systems particularly those for use by an aircraft pilot to view the surrounding terrain from a more favorable vantage point than the cockpit.
More particularly, the invention pertains to a vision display system that presents to the pilot or operator both a biocular view of the scene and a binocular view of the scene from a display mounted on a helmet.
2. Description of the Prior Art
When a scene is viewed from a single position and is presented to the observer at both eye positions the view lacks the perception of depth, the third dimensional effect. A scene viewed in this way is called biocular. However, when a single scene is viewed from two positions spaced even slightly from one another the view presented to the observer has the sense of depth. A scene viewed in this way is called binocular. A scene viewed from one eye position and produced from one position is called monocular and lacks the third dimensional effect. Biocular and monocular display systems necessarily produce relatively narrow fields of view.
However a pilot requires a wide field of view, particularly when looking leftward or rightward from center, whereas when looking forward a relatively narrow field of view horizontally is acceptable.
Monocular scene generators can be used to produce a biocular system but the result is restricted to a narrow field of view, and one lacking the requisite third dimension effect.
When a helicopter accelerates during flight from hover to high forward speed, the attitude of the fuselages pitches nose down as much as 40 degrees. Therefore, a visual display system for use by a helicopter pilot should have a wide vertical field of view when looking forward so that the surrounding terrain can be seen both in the hover attitude and the high forward speed attitude.
Furthermore, the pilot should have a wide horizontal field of view when the aircraft is in both the nosedown and hover attitudes. Preferably the pilot's view from the display will permit adequate differentiation between objects at various distances from the camera that is used to produce the picture seen by the pilot.